1. Field of the Invention
The present invention relates to task lighting systems and, more particularly, to an improved means for evenly distributing light with reduced glare over an entire work surface using a single panel having integral lens and diffuser functions.
2. Description of the Related Art
Light from a linear source, such as a conventional fluorescent bulb mounted over a work surface, has an uneven illumination pattern. That is, the light is directed primarily to a center of the work surface, with greatly reduced illumination of the front, rear and sides of the work surface. Typically, a lens is employed to provide more uniform illumination across the work surface from one side to the other.
Strong coherent illumination also produces considerable glare off the work surface. Glare is undesirable because it causes fatigue, eye strain, and reduced user efficiency. In addition, direct light or glare from the bulb, such as caused by the user viewing the bulb, is very distracting and can cause fatigue.
Oftentimes a separate frosted diffuser sheet is employed to reduce glare by dispersing and attenuating light emanating from the light source. Frosted diffusers randomly diffuse light, thereby reducing glare or veiling reflections. However, because frosted diffusers randomly diffuse the light without attempting to focus it, they fail to adequately and uniformly illuminate the work surface from front to rear. Moreover, although frosted diffusers can prevent the user from viewing the bulb, a substantial amount of light still impinges on the user's eyes directly from the bulb. Further, the light is still reflected from a work surface to a user's eyes even though the light is diffused and attenuated.
Some diffusers employ prismatic refractors in an attempt to reduce glare and disperse light. An example of such an arrangement is disclosed in U.S. Pat. No. 4,233,651, issued Nov. 11, 1980 to W. Fabbri which discloses a lower refractor plate that is slidable laterally relative to an upper refractor plate. While light is dispersed toward opposite side portions of the work surface when the lower refractor plate is centered relative to the upper plate, only the central portion of the work surface is provided with glare-free light. The Fabbri structure is not adapted to prevent light from the source from directly impinging on the user's eyes or to prevent the source from being viewed by the user. The user can still view end portions of the light source. Further, the upper refractor plate increases the cost of the diffuser substantially.
U.S. Pat. No. 4,300,185 issued Nov. 10, 1981 to J. Wakamatsu discloses a structure in which the lighting fixture must be positioned above the front edge of the work surface. A control lens includes a plurality of pyramidal indentations formed adjacent to a front edge of and on an upper surface of the lens, the indentations being adapted to disperse light. The remainder of the upper surface is covered by a plurality of longitudinally extending linear indentations of nonuniform depth. However, the disclosed embodiments do not block direct viewing of the light source by a user or prevent light from directly impinging on the user's eyes.
Thus, there is a need for an improved task light panel that evenly disperses light over a work surface, reduces glare from the work surface, and effectively blocks the user's direct view of the light source. It would be advantageous if a single panel having these capabilities could be provided as this would reduce the production and assembly costs of a task lighting system.